1. Field of the Invention
The present invention relates to a process for preparing alkyl nitroacetates. More particularly, it relates to a process for preparing alkyl nitroacetates by reacting a nitroparaffin with an alkyl phenyl carbonate in the liquid phase.
2. Description of the Prior Art
Alkyl nitroacetates are useful compounds for preparing alpha-nitrocarboxylic acids by reacting the same with alkyl halide, aldehyde, tertiary amines, and the like. It is also well known that production of amino acids such as phenyl alanine, dopa, methyl dopa, tryptophan, alpha-methyltryptophan, etc. is easily carried out by hydrogenating alpha-nitrocarboxylic acids.
There are known various processes for preparing alkyl nitroacetates. For example, (1) Kornblum et al reported in J. Amr. Chem. Soc., 77, 6654 (1955) that ethyl nitroacetates were obtained by reacting ethyl iodoacetate with silver nitrite; (2) Kinkseiner and his coworkers reported in J. Org. Chem., 28, 215 (1963) that a magnesium complex of nitroacetic acid was obtained by reacting nitromethane with methyl carbonate magnesium, which was then subjected to esterification to obtain a nitroacetic acid ester using a strong acid; (3) Zen et al reported in J. Chem. Soc. of Japan, Ind. Chem. Sec., 74, 70 (1971) that methazonic acid salt was obtained by reacting 2 moles of nitromethane with 8 moles of potassium hydroxide, which was then esterified to obtain a nitroacetic acid ester using a strong acid; and (4) Sifniades and others disclosed in J. Org. Chem., 40, 3562 (1975) that a nitroacetoacetic acid ester was obtained by reacting an acetozcetic acid ester with an acyl nitrate, which was then decomposed with an alcohol to obtain a nitroacetic acid ester.
Among the processes mentioned above, the process (2) is not practical as it involves the use of expensive silver salt and metal of magnesium as the starting materials. It is also difficult to put the process (3) to a large scale application as the reaction requires heating of alkali metal salts of nitromethane which entails the dangerous detonation. The process (4), further, necessitates the use of relatively expensive materials such as acetoacetic acid ester and acyl nitrates.